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User blog:Samuli.seppanen/Back in business
It has been a while (over 6 months) since I actively worked on the cheiroballistra. Some weeks ago I finished my new workshop and, after a few detours1, was able to resume the work on the cheiroballistra. Over the last few days I've fixed a large number of minor issues in the cheiroballistra. Wooden shims were added between the little ladder tenons and the pi-brackets under the wedges: The shims should help with two things: * The slow loosening of the wedges due to little ladder tenon movement * Slipping of the field-frame bars from the notches in the tenons A pair of pins was added to each end of the little arch to rigidify the upper part of the field-frames. The holes in the Orsova little arch may be explained with similar pins: The elliptically tillered arms with heavily rounded, rectangular cross-section are also finished: These new arms should be tons of stronger than the earlier linearly tapering arms. The weight difference is only about 10%, while the strength increase is probably 100% or more. Shallow grooves were added to the sides of the cones for the metal hoops: This should prevent the hoops from moving due to the pressure from the torsion spring. While hoop slippage has not been a severe problem in the past, it had the potential to become one as spring pretensioning is increased. The grooves do not violate any wood fibers that would be under any significant stress during pullback, and thus should not make the cones noticeably weaker. I also made some minor changes to the (temporary) pulling handle and the locking pin to allow forceful pullback and auto-locking. Here's the handle in action: A few things still need to be fixed before full-power shooting: * Saw off a triangular piece from the front end of the case to allow near full-draw tests even on soft ground (more discussion) * Bind the handle axle to "something closer to the front" just in case the end grain of slider decides to break I'm also thinking of adding some (non-authentic) dynema safety cords to the arms to prevent them from completely disintegrating should they break. In retrospect this should have been done before the hoops and the wrappings were attached. In theory, a cone breakage should be fairly "harmless", meaning that the arm would only contain a very small percentage of the energy of the torsion spring. However, there is always the possibility of the other arm swinging the broken arm to my face at high speed - a prospect I'd like to avoid. At minimum, the full power tests will require lots of head, eye and chest protection. Also note that many of the existing Wiki HOWTO articles were updated with new information. Some new ones were also added. See the to see what has been happening. 1 Two new crossbows with all-wooden bows, making tons of bolts and doing some staff-sling testing Category:Blog posts Category:Backup Category:Arms Category:Little ladder Category:Little arch Category:Lock